全文获取类型
收费全文 | 4138篇 |
免费 | 34篇 |
国内免费 | 21篇 |
专业分类
安全科学 | 76篇 |
废物处理 | 282篇 |
环保管理 | 304篇 |
综合类 | 431篇 |
基础理论 | 848篇 |
环境理论 | 7篇 |
污染及防治 | 1545篇 |
评价与监测 | 415篇 |
社会与环境 | 272篇 |
灾害及防治 | 13篇 |
出版年
2023年 | 54篇 |
2022年 | 117篇 |
2021年 | 184篇 |
2020年 | 76篇 |
2019年 | 69篇 |
2018年 | 152篇 |
2017年 | 163篇 |
2016年 | 234篇 |
2015年 | 120篇 |
2014年 | 243篇 |
2013年 | 388篇 |
2012年 | 281篇 |
2011年 | 301篇 |
2010年 | 227篇 |
2009年 | 162篇 |
2008年 | 226篇 |
2007年 | 270篇 |
2006年 | 193篇 |
2005年 | 156篇 |
2004年 | 109篇 |
2003年 | 93篇 |
2002年 | 91篇 |
2001年 | 53篇 |
2000年 | 41篇 |
1999年 | 26篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1970年 | 2篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1964年 | 5篇 |
1962年 | 3篇 |
1959年 | 4篇 |
1958年 | 15篇 |
1957年 | 5篇 |
1955年 | 2篇 |
排序方式: 共有4193条查询结果,搜索用时 62 毫秒
921.
Jonathan Mark Wilson Alexandre Leitão Ana Filipa Gonçalves Catarina Ferreira Patrick Reis-Santos Ana-Violeta Fonseca Joana Moreira da Silva José Carlos Antunes Cristina Pereira-Wilson João Coimbra 《Marine Biology》2007,151(5):1633-1645
The Anguillid juvenile glass eel must deal with the osmoregulatory consequences of highly variable environmental salinities
on its recruitment migration from coastal to fresh waters. Changes in ionoregulatory parameters and branchial ion transport
protein [Na+/K+-ATPase, Na+:K+:2Cl− cotransporter (NKCC), cystic fibrosis transmembrane regulator (CFTR) anion channel, V-type proton ATPase] expression (activities,
protein and/or mRNA level expression and/or cellular localization) in response to acclimation to a broad range of ionic strengths
[distilled water (DW) to hypersaline water (HSW; 150%) sea water (SW 32‰)] was studied. The estuarine glass eels were very
euryhaline and successfully acclimated to acute changes in environmental ionic strength from 50% SW, with high mortality only
observed in HSW (51%) and sublethal osmoregulatory indicators (whole body water content and sodium levels) disturbed at the
extremes (DW and HSW). Central to a high salinity acclimation were elevated branchial Na+/K+-ATPase, NKCC and CFTR expression. At lower salinity, Na+/K+-ATPase expression was maintained and NKCC and CFTR expressions were reduced. Branchial chloride cells increased in size up
to SW but decreased in HSW. During hypotonic disturbance (DW), no compensatory elevation in V-ATPase or Na+/K+-ATPase expression was observed. 相似文献
922.
Copulatory plugs do not assure high first male fertilisation success: sperm displacement in a lizard
Pedro L. Moreira Vera L. Nunes José Martín Octávio S. Paulo 《Behavioral ecology and sociobiology》2007,62(2):281-288
Sperm competition selects for opposing male defensive and offensive reproductive traits, and its outcome may be determined
by the effectiveness to which one trait has evolved to out-compete the other. We tested the effectiveness of a first male
plug physical interference with a second male insemination (defence) vs the effectiveness of plug and associated sperm displacement
by a second male (offence) on the outcome of sperm competition in Iberian rock lizards. We conducted a double mating experiment
where we compared the proportion of eggs per clutch fertilised by the same second males (against the same first males) when
they copulated with females 30 min (first male plug adhered firmly inside the female cloaca) and 4 h (first male plug loosely
adhered or shed from the female cloaca) after first males. We found that second males fertilised the majority of the eggs
per clutch in the 30-min treatment, whereas fertilisations were equally shared between the two males in the 4-h treatment.
These results show that plugs have little defensive effectiveness, and thus, do not assure high first male fertilisation success.
Instead, sperm displacement appears to be associated with plug displacement. That is, because sperm embedded in first male
plugs, and displaced from competition for fertilisations by second males, is expected to increase in number with decreasing
time allowed for female sperm transport, second males thus enjoy higher fertilisation success. This study shows that offensive
plug displacement out-competes plug defensive role in Iberian rock lizards. Moreover, it reveals sperm displacement as a novel
sperm competition mechanism in reptiles. 相似文献
923.
Roles of male residence and relative size in the social behavior of Iberian rock lizards, Lacerta monticola 总被引:2,自引:0,他引:2
Many studies on contest competition used residency asymmetry as a discrete variable. However, the probability of winning an
interaction may change as a continuous function of the value of the location where the encounter occurs. We performed a field
study to examine the importance of location within a home range and relative body size to the outcomes of agonistic interactions
between male lizards, Lacerta monticola. The distances to activity centers (the most used locations based on a density function of sightings) and relative size play
important roles in agonistic interactions and had interacting effects in natural conditions. On the other hand, previous studies
with lizards suggested that inferior competitors are able to avoid agonistic interactions in the field. Thus, we staged encounters
in the laboratory to examine the behavioral responses of smaller individuals. The responses of each focal smaller male were
measured in its own home cage (resident), in the cage of a larger male (intruder) and in a cage in which no male was previously
present (control). The predominant behavioral tactics of smaller males were avoidance when they are the intruders and displaying
when they are the residents. Submissive displays by smaller males may help reduce the costs of agonistic encounters. 相似文献
924.
Celia A Harvey Arnulfo Medina Dalia Merlo Sánchez Sergio Vílchez Blas Hernández Joel C Saenz Jean Michel Maes Fernando Casanoves Fergus L Sinclair 《Ecological applications》2006,16(5):1986-1999
As tropical regions are converted to agriculture, conservation of biodiversity will depend not only on the maintenance of protected forest areas, but also on the scope for conservation within the agricultural matrix in which they are embedded. Tree cover typically retained in agricultural landscapes in the neotropics may provide resources and habitats for animals, but little is known about the extent to which it contributes to conservation of animal species. Here, we explore the animal diversity associated with different forms of tree cover for birds, bats, butterflies, and dung beetles in a pastoral landscape in Nicaragua. We measured species richness and abundance of these four animal taxa in riparian and secondary forest, forest fallows, live fences, and pastures with high and low tree cover. We recorded over 20,000 individuals of 189 species including 14 endangered bird species. Mean abundance and species richness of birds and bats, but not dung beetles or butterflies, were significantly different among forms of tree cover. Species richness of bats and birds was positively correlated with tree species richness. While the greatest numbers of bird species were associated with riparian and secondary forest, forest fallows, and pastures with >15% tree cover, the greatest numbers of bat species were found in live fences and riparian forest. Species assemblages of all animal taxa were different among tree cover types, so that maintaining a diversity of forms of tree cover led to conservation of more animal species in the landscape as a whole. Overall, the findings indicate that retaining tree cover within agricultural landscapes can help conserve animal diversity, but that conservation efforts need to target forms of tree cover that conserve the taxa that are of interest locally. Preventing the degradation of remaining forest fragments is a priority, but encouraging farmers to maintain tree cover in pastures and along boundaries may also make an important contribution to animal conservation. 相似文献
925.
Sergio Rodríguez Xavier Querol Andrés Alastuey Jesús de la Rosa 《Environmental Chemistry Letters》2007,5(1):1-7
This article synthesises the results obtained in several projects on atmospheric aerosol (particulate matter – PM) pollution
developed during the last years in the Western Mediterranean. It focuses on particulate matter sources and the strategies
for suitable monitoring in ambient air. The article has been structured in several sections that give response to the main
questions that prompted these studies. After analysing the main PM features in the Mediterranean, a brief review of the main
factors differentiating the particulate matter composition with respect to Central Europe is presented. Finally, the suitability
of the different metrics or parameters for monitoring ambient air PM levels in different types of environments is discussed.
Selected article from the 6th European Meeting on Environmental Chemistry, University of Belgrade, Serbia and Montenegro organized
by Prof. Dr. Branimir Jovancicevic (www.research.plymouth.ac.uk/ace). 相似文献
926.
J.?MartínEmail author P.?López W.?E.?CooperJr. 《Behavioral ecology and sociobiology》2003,54(5):505-510
Because time spent in refuge may be costly if prey lose opportunities to forage, fight, or mate, prey allow predators to approach closer before beginning to flee when opportunity costs are high. Because the same opportunity costs may apply to refuge use as to escape, prey should make similar trade-offs between risk of emerging and cost of remaining in refuge. In the Iberian rock lizard, Lacerta monticola, we studied the effects of sex, reproductive season, speed of predator approach, and potential loss of mating opportunities on time spent in refuge following simulated predatory attacks. Lizards of both sexes adjusted refuge use to the level of risk by spending more time in refuge when approached rapidly than slowly. Females remained in refuge for equal times in the mating and postreproductive seasons, but males emerged sooner during the mating season, suggesting adjustment to a cost of lost opportunity to search for mates during the mating season. When a tethered female was nearby, males emerged from refuge earlier than if no female was present, indicating a trade-off between risk and mating opportunity. Approach speed affected emergence time when females were absent, but not when a female was present. Approach speed did not affect the probability that, after emerging, a male would return to court the female. For males that courted females intensely (bit them) before entering refuge, approach speed did not affect latency to emerge, but males that courted less intensely emerged sooner if approached slowly than rapidly. These findings show that males adjust the length of time spent in refuge to both risk of predation and reproductive cost of refuge use.Communicated by A. Mathis 相似文献
927.
Female preference for dominant males is widespread and it is generally assumed that success in male-male competition reflects high quality. However, male dominance is not always attractive to females. Alternatively, relatively symmetric individuals may experience fitness advantages, but it remains to be determined whether males with more symmetrical secondary sexual traits experience advantages in both intra- and intersexual selection. We analysed the factors that determine dominance status in males of the lizard Lacerta monticola, and their relationship to female mate preference, estimated by the attractiveness of males' scents to females. Sexually dimorphic traits of this lizard (head size and femoral pores) appear to be advanced by different selection pressures. Males with relatively higher heads, which give them advantage in intrasexual contests, were more dominant. However, head size was unimportant to females, which preferred to be in areas marked by relatively heavier males, but also by males more symmetric in their counts of left and right femoral pores. Chemicals arising from the femoral pores and other glands might honestly indicate quality (i.e. related to the symmetry levels) of a male to females and may result from intersexual selection. Females may use this information because the only benefit of mate choice to female lizards may be genetic quality. Chemical signals may be more reliable and have a greater importance in sexual selection processes of lizards than has previously been considered. 相似文献
928.
Antonio G. Checa Concepción Jiménez-López Alejandro Rodríguez-Navarro Jorge P. Machado 《Marine Biology》2007,150(5):819-827
To understand the relative importance of biological versus physicochemical control over biomineralization, we have tested
if the chemical composition of the medium (i.e., the Mg/Ca ratio) can change the mineralogy of mollusk shells. The shells
of mollusks are made of calcite and/or aragonite, which are by far the most common CaCO3 polymorphs. Several species of bivalves with predominantly calcitic shells have been cultivated in artificial seawater with
a Mg/Ca molar ratio within the range of 8.3–9.2, well above the present value for seawater (5.2). Four out of six species
used (the scallop Chlamys varia, the oyster Ostrea edulis, the saddle oyster Anomia ephippium and the mussel Mytilus edulis) survived long enough to secrete significant amounts of calcium carbonate. The deposits (sometimes extensive) formed on the
interior shell surfaces were predominantly aragonitic. Three individuals of C. varia also increased their length by adding new shell at the margin. Contrary to the internal shell deposits, these margins were
high-Mg calcite. This implies that the marginal mantle is able to exert a more strict control on the secreted mineral phase
than the mantle facing the internal shell surface. This is the first report on an in vivo experimentally forced switch in
bivalve shell mineralogy, from calcite to aragonite due to a change in water chemistry. 相似文献
929.
Abstract Festuca rubra L. plants are pseudometallophytes colonizing abandoned Pb/Zn mine areas, successfully employed in phytostabilization. To study the contribution of low-molecular weight organic acids to metal tolerance, F. rubra plants were grown for three months in hydroponics with Cd (1.8, 18 and 36 µmol?L?1), Pb (50, 250 and 500?µmol?L?1) and Zn (0.3, 3 and 6?mmol?L?1), separately, and in ternary combination (18?µmol?L?1 Cd + 250?µmol?L?1 Pb + 0.3?mmol?L?1 Zn). The roots retained most of the metals but their distribution from shoot to root was altered when the plants were treated with the ternary combination. The main organic acids in roots were citrate and malate. At the lowest concentrations, the metals caused small reductions in biomass, had no effects on photosynthetic pigments nor on malondialdehyde, but led to increases in root organic acids. At higher concentrations, phytotoxic responses were observed, associated with a decline of citrate and malate in the roots. 相似文献
930.
J. C. Coll B. F. Bowden G. V. Meehan G. M. Konig A. R. Carroll D. M. Tapiolas P. M. Aliño A. Heaton R. De Nys P. A. Leone M. Maida T. L. Aceret R. H. Willis R. C. Babcock B. L. Willis Z. Florian M. N. Clayton R. L. Miller 《Marine Biology》1994,118(2):177-182
This paper provides the first evidence for sperm chemotaxis in the Scleractinia. Montipora digitata Dana, 1845 (Scleractinia: Coelenterata) is a hermaphroditic coral which reproduces bi-annually, releasing egg-sperm bundles during the mass spawning at Magnetic Island (19°10S; 146°52E) in late spring-early summer, and autumn each year. The buoyant egg-sperm bundles float to the surface where they break apart, releasing eggs and sperm into the ocean. Fertilisation occurs after 30 min. Unfertilized eggs were collected, washed free of sperm, and freeze-dried. The eggs were extracted with dichloromethane, fractionated by chromatography on silica gel, and the fractions assayed for their ability to attract M. digitata sperm. The active fraction was further fractionated by high-performance liquid chromatography, resulting in the isolation of three highly unsaturated fatty alcohols: (1) dodeca-2,4-diynol; (2) tetradec-13-ene-2,4-diynol; (3) (14Z)-heptadeca-14,16-diene-2,4-diynol. Of these three compounds, only Compound 1 attracted sperm of M. digitata. Synthetic Compound 1, produced from simple precursors by known reactions, possessed sperm-attracting activity comparable to the naturally derived attractant. Preliminary experiments suggest that the natural mixture of Compounds 1, 2 and 3 in the ratio 1:4:9 is more effective in attracting sperm from M. digitata than sperm from other Montipora species. Sperm attractants may act to reduce the incidence of hybridisation between different species of Montipora. 相似文献